Functioning grouped soil microbial communities according to ecosystem type, based on comparison of fallows and meadows in the same region.

ABSTRACT

Predicting the composition and function of microbial communities at a bio-geographical scale, across ecosystems, is challenging. We compared six abandoned fields to six meadows to see whether soil microbial community structure and activity are more similar within the ecosystem type than between the types. We implemented bacteria and fungi phylogenetic markers profiling, phospholipids analysis, fluorescence counts of total bacteria and algae and microscopy of arbuscular mycorrhizal fungi (AMF). The functional performance of microbial communities was assessed using enzymes activity measurements as well as culturing and incubation experiments. The studied fallows and meadows had similar biomass and general structure of soil microbial communities. However, the AMF root colonization frequency was higher in the meadows than in the fallows. The AMF colonization was promoted in meadows characterised by lower availability of NO3-, P and K as well as higher soil pH, which additionally hampered plant acquisition of P at the P-limited ecosystem. Fallow and meadow microbial communities showed characteristic functional traits. Meadow soils exhibited higher basal respiration rate, while cellulose decomposition and nitrogen mineralization were faster in fallows. Even when no major differences in community structure could have been detected soil microbial communities adapted to local and/or instantaneous environmental conditions and formed functionally-specific ecotypes. This work points out the relevance of preserving meadows as reservoirs of plant diversity, which cope excellent in nutrient depleted conditions and in mountain regions thanks to microbial components of ecosystem.